[draco] Can't link drakodec.lib with target_link_libraries, usage file missing

[MrROBUST]

Hello, after installing this library in vcpkg, it doesn't show how to use it.

I am trying to use the [draco] decoding support of the [tinygltf] library with this simple program example (main.cpp):

#include <nlohmann\json.hpp>

#define TINYGLTF_NO_STB_IMAGE
#define TINYGLTF_NO_STB_IMAGE_WRITE
#define TINYGLTF_IMPLEMENTATION
#define TINYGLTF_NO_INCLUDE_JSON
#define TINYGLTF_ENABLE_DRACO
#include <tiny_gltf.h>

int main()
{
  using namespace tinygltf;

  Model model;
  TinyGLTF loader;
  std::string err;
  std::string warn;

  if (!loader.LoadBinaryFromFile(&model, &err, &warn, "models/viking_room.glb"))
  {
    throw std::runtime_error(warn + "\n" + err);
  }

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required (VERSION 3.8)

project(TinyGltfDraco)

add_executable(TinyGltfDraco main.cpp)

set_target_properties(TinyGltfDraco
PROPERTIES
  CXX_STANDARD 17
  CXX_EXTENSIONS OFF
)

find_package(nlohmann_json CONFIG REQUIRED)
target_link_libraries(TinyGltfDraco PRIVATE nlohmann_json nlohmann_json::nlohmann_json)

find_path(TINYGLTF_INCLUDE_DIRS "tiny_gltf.h")
target_include_directories(TinyGltfDraco PRIVATE ${TINYGLTF_INCLUDE_DIRS})

The project is built by Cmake using the vcpkg toolkit. Building with the Visual Studio 2019 compilers generates some linkage errors:

[build] main.cpp
[build] main.obj : error LNK2019: unresolved external symbol "public: __cdecl draco::Options::Options(void)" (??0Options@draco@@qeaa@XZ) referenced in function "public: __cdecl draco::DracoOptions::DracoOptions(void)" (??0?$DracoOptions@W4Type@GeometryAttribute@draco@@@draco@@qeaa@XZ) [%path%\build\TinyGltfDraco.vcxproj]

It looks like Draco header files can be found automatically with no additions to CMakeLists, but dracodec.lib or draco.lib is not passed to the linker.

If I add these lines to CMakeLists:

find_package(Draco CONFIG REQUIRED)
target_link_libraries(TinyGltfDraco PRIVATE draco)

I got that error:

[build] LINK : fatal error LNK1104: cannot open file 'draco.lib' [%path%\build\TinyGltfDraco.vcxproj]

But something like this works (for a debug build):

find_package(Draco CONFIG REQUIRED)
target_link_libraries(TinyGltfDraco PRIVATE "${draco_LIBRARY_DIR}/../debug/lib/dracodec.lib")

I am wondering if I am doing something wrong or the port is missing some exports?

Additional context:
Draco's github page says we need to link the draco_dec (https://github.com/google/draco#c-decoder-api) but it's probably a typo (https://stackoverflow.com/questions/62313136/how-to-include-the-draco-dec-library). I have both draco.lib and dracodec.lib working so I'm not sure what should be linked by default. Should these be separate targets, like: target_link_libraries(TinyGltfDraco PRIVATE draco::draco) or target_link_libraries(TinyGltfDraco PRIVATE draco::dracodec)?

[NancyLi1013]

Hi @MrROBUST

Thanks for posting this issue.

Seems there are some problems when using find_package() in draco. I will investigate and try to fix this later.

[JackBoosY]

I think draco expoted DracoConfig.cmake is incomplete. It only contains difficult macros.

[LesleyLai]

Draco updated to 1.5.0 and reworked its find_package support in this PR. Probably that will fix the issue once vcpkg supports Draco 1.5.0

[JackBoosY]

@LesleyLai No it wasn't.
The draco-config.cmake still can't be used in Windows.

[JackBoosY]

I opened a PR to the upstream to fix this issue: google/draco#787
Let's see what happened.

[LesleyLai]

Thank you for doing this!

[Tradias]

Since draco 1.5.3 there is now a proper dracoConfig.cmake + dracoTargets.cmake which support imported targets. The usage information is also helpful now:

 draco provides CMake targets:
 
     # this is heuristically generated, and may not be correct
     find_package(draco CONFIG REQUIRED)
     target_link_libraries(main PRIVATE draco::draco)

See #27145